Hi Peter & All,
There's another way of viewing closed/open world assumptions.
It's to posit that attempting to model a real situation using only these
assumptions is sort of like flying a plane using only 2-dimensional
information.
There's a dimension missing, and that leads at best to messy modeling.
A cleaner approach, one that may be useful in many practical situations, is
to add the missing dimension -- namely *Time*.
If we add a time stamp to each update, be it an addition or a removal, then
we can reason over data using only the closed world assumption, and we can
give results in the form "*as of <time> the data led to this answer.*"
HTH,
-- Adrian
Internet Business Logic
A Wiki and SOA Endpoint for Executable Open Vocabulary English Q/A over SQL
and RDF
Online at www.reengineeringllc.com
Shared use is free, and there are no advertisements
Adrian Walker
Reengineering
On Tue, Aug 21, 2012 at 6:11 PM, <Peter.Hendler@kp.org> wrote:
> That's actually quite interesting and clarifies a foggy little place in my
> head. It does bring up the question of "who knows when to use the RDF they
> find as Open or Closed world?. It might be something that only depends on
> what you, the user, want out of it. I don't know if you'd always have to
> know under what circumstances it was collected. For example, all created
> by one person or collected over the internet by anyone who wanted to
> contribute to it.
>
> If it was "created" open world, and queried closed world, or visa versa,
> would that matter much?
>
> Now FHIR is specifically a very interesting case and might be an
> exception. FHIR is closed world in it's creation. It is very carefully
> created by a close group of authors that are working together and agreeing.
> So it is definitely closed world. Maybe it is safe to use RDF with closed
> world queries in this case because it is already known to be closed world.
> You do have the "unique naming assumption" in play for example.
>
> In other words, my question is. Can you use RDF in a closed world way
> when ever you want, or is it only safe when the model you're dealing with,
> like FHIR, really is known to be closed world?
>
>
>
>
>
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>
>
> *David Booth <david@dbooth.org>*
>
> 08/21/2012 02:33 PM
> To
> Peter Hendler/CA/KAIPERM@KAIPERM
> cc
> mscottmarshall@gmail.com, helena.deus@deri.org,
> kerstin.l.forsberg@gmail.com, LINMD.SIMON@mcrf.mfldclin.edu,
> meadch@mail.nih.gov, public-semweb-lifesci@w3.org, ratnesh.sahay@deri.org
> Subject
> Re: seeks input on Study Data Exchange Standards An alternative approach
>
>
>
>
> Hi Peter,
>
> Very nice observations! I wholeheartedly agree with your basic thesis,
> but I would quibble with one off-hand remark . . .
>
> On Tue, 2012-08-21 at 08:47 -0700, Peter.Hendler@kp.org wrote:
> > Sorry I didn't make the meeting but just looked at the minutes.
> >
> > We (Kaiser) do use the Ontology features of SNOMED extensively and
> > have a different take on how it should be done.
> >
> > Specifically we would not advocate for example, putting FHIR in RDF or
> > OWL. What we've found to be simple, useful, and very clean is to
> > recognize the two different kinds of logic involved.
> > And keep them isolated to different parts of the model.
> >
> > Intensional (like OWL, Open World, Reasoners and inferences)
> > Extensional (like HL7 openEHR all Object Oriented models, all
> > databases)
>
> While I completely agree with the basic idea of being selective in the
> use of inference, and in your rule-of-thumb in separating intensional
> from extensional, I disagree that putting FHIR in RDF would be a bad
> idea.
>
> Representing data in RDF does not mean that any sort of inference
> *must* be done, though it does enable inference if you *choose* to do
> so. RDF can certainly be used merely as a flexible, schema-less data
> model, using the closed world assumption (CWA), purely for data
> integration purposes, and it is very good for this. But it is important
> to know which data is being used this way and which is being used under
> the open world assumption, and I think your observations on this are
> very good.
>
> Best wishes,
>
> --
> David Booth, Ph.D.
> http://dbooth.org/
>
> Opinions expressed herein are those of the author and do not necessarily
> reflect those of his employer.
>
>
>
>
>